Testing Network Software Part I
Exploring Tools available for testing and managing network connections
Objectives
Advanced Understanding of Ping Using Tracert Using ICMP Netstat switches Ipconfig switches Route Print Command Using Network Monitor
Packet Internet Groper : PING
A connection testing tool Functions at application layer Uses ICMP (Internet Control Message Protocol)
Network Layer protocol ICMP = protocol 1 in packet header Windows Firewall blocks protocol 1 by default
Need to disable the Windows Firewall for using ping or tracert
Ping responses can be tweaked by using the various switches for additional information
Using PING advanced options
ICMP offers information on:
Packet size Connection status TTL Time Stamps Time for response in milliseconds
Can be used in:
default mode
Defined echo requests/replies
extended mode
Can change the number of ping requests, length of packets, etc.
Some ICMP Control Messages
0 - Echo Reply 3 - Destination Unreachable 4 - Source Quench 5 - Redirect Message 6 - Alternate Host Address 8 - Echo Request 9 - Router Advertisement 10 - Router Solicitation 11 - Time Exceeded 12 - Parameter Problem
15 - Information Request 16 - Information Reply 17 - Address Mask Request 18 - Address Mask Reply 19 - Reserved for security 20-29 - Reserved for robustness experiment 30 - Traceroute 31 - Datagram Conversion Error 32 - Mobile Host Redirect 33 - IPv6 Where-Are-You 34 - IPv6 Here-I-Am 35 - Mobile Registration Request 36 - Mobile Registration Reply 38 - Domain Name Reply 39 - SKIP Algorithm Discovery Protocol 40 - Photuris, Security failures 41 - ICMP for experimental mobility protocols such as Seamoby [RFC4065]
14 - Timestamp Reply
13 - Timestamp
Live Ping Lab
Note the /? to find additional ping options, aka switches
Ping -t
The `t' switch extends the ping to an indefinite number of `echo requests' Control + C keys will stop the process How could this extra information be useful? What other information do you glean from this output?
Ping a [ip address]
Resolves ip address to FQDN Tells you what the host computer name is Tells you what the network suffix name is
Ping lab
Ping Lab 10 minutes Students should use all the switches and compare the results Have everyone ping a single student's computer
Use multiple instances of ping (multiple command screens) Extend length to 65000 Unlimited ping requests
Have target student report
the status of the network connection status received bytes / sent The task managernetwork performance changes
ipconfig
Mostly used to verify settings
IP address Subnet Mask Default Gateway Physical Address DNS Server WINS Server
Can detect the presence of multiple network interfaces
Ipconfig /?
Switches allows more than just displaying settings
Ipconfig lab
Disconnect students from internet Have them try to reach www.gooffcampus.com Reconnect the Internet Can they reach the website? Open command prompt
Use ipconfig /flushdns to clear dns cache
Have them try to reach the site again Explain what happened
Ipconfig continued
Ipconfig /release Ipconfig
What happened to the ip address
Ipconfig /renew Ipconfig
Did the ip address come back? Is it the same as before?
What would happen if you changed the NIC settings to a manual address and repeated the commands above?
Local Machine Routing of IP
Machines can have multiple interfaces
Physical
LAN Nic(s) Modem
Virtual
Loopback
Each interface can lead to a different network or have a different function
Function of loopback is internal testing of TCPIP software
How PCs route data to a network
When a PC needs to communicate with another PC or perhaps a web server it needs to be told how to get there The big question:
Is it on a local network or a remote one?\ If local use the local interface If remote use the default gateway
A PC can be connected to multiple networks
Multiple NICS or Multiple addresses on the same NIC The question proc...